> I'll pay any amount of money that will make me sit down and do things.

That's almost exactly what I said to myself that prompted me to realize I needed to go to a doctor. Not because I planned on actually spending any amount of money, but because that level of sheer desperation is what finally convinced me I had something wrong with me.

Turns out I had undiagnosed and untreated ADHD the whole time. I'd seek a second opinion because I have no idea why your doctor would say you "definitely don't have ADHD" unless he is one of those doctors that just doesn't believe in ADHD, which is unfortunately common. If you weren't rigorously tested then that doctor's opinion doesn't mean anything, so try again.